Energy saving controller

ABSTRACT

A method for controlling an air handler including a fan and a heater or a compressor, the method including installing an energy saving controller (“ESC”) between a thermostat and the air handler, monitoring by the ESC of ON and OFF durations of the heater if the air handler is in a heating mode, or the compressor if the air handler is in cooling mode, in a first cycle and of ON duration of a second cycle, and determining the fan&#39;s first run time extension amount based on the ON and OFF durations of the first cycle and the ON duration of the second cycle.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part and claims the benefit ofU.S. Non-Provisional application Ser. No. 14/016,012, filed Aug. 30,2013, and U.S. Non-Provisional application Ser. No. 14/332,714, filedJul. 16, 2014, which are hereby incorporated by reference, to the extentthat they are not conflicting with the present application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to energy saving devices and methods forHVAC systems and particularly to a plug and play energy savingcontroller (ESC) to predict and extend the fan run time of HVAC systemsafter the heating or cooling unit has shut off and/or to stop thecompressor or heater for a short duration of time if the compressor orheater has been running continuously for fixed periods of time, whilethe fan is still blowing.

2. Description of the Related Art

Conventional HVAC (Heating Ventilating and Air Conditioning) systemsinclude temperature changing components for changing the temperature andcondition of air. Indoor air handlers drive air from the temperaturechanging component through supply ducts to zones within a building. Atypical HVAC consists of heating unit, air conditioning or cooling unitor heat pump unit, and the fan or blower at the air handler unit. Athermostat is used to control the conditions of the air in a conditionedspace by sending control signals to the HVAC's relays or contactors toactivate or deactivate one or more of the temperature changingcomponents.

Conventional HVAC typically runs the ventilation fan for an additional 0second to 90 seconds after the furnace or air conditional compressor hasbeen turned off.

Studies have shown that even after this 90 seconds duration, the furnacesurface and the air conditioner cooling coil still has some energy left.For example, most furnace heat exchangers are still hot (above 135 to210° F.) after the furnace fan turns off. This wasted energy is notdelivered to the conditioned space when the fan stops blowing.

Studies have also shown that if the cooling unit has been runningcontinuously for a period of time of 20 minutes to 30 minutes, thecooling coil is wet and the evaporating of the water from the wet coilcan provide additional cooling energy that can be harnessed. Also, ifthe heating unit has been running continuously for a period of timeapproximately 20 to 30 minutes, the furnace is at its maximumtemperature, and by shutting down the furnace for a short period oftime, but letting air flowing through it, it will not only reduce thefurnace temperature therefore extending its life, but also harvest someresidual heat energy for the conditioned room.

Therefore there is a need for a plug and play energy saving controllerthat can easily be inserted between the thermostat and the air handlerof an HVAC system to recover additional heating and cooling capacity andoperate HVAC equipment at higher efficiency.

There are many manufacturers of thermostats where the fan output commandsignal goes into a floating or unknown state when the thermostat is shutoff by putting the thermostat switch to system off. In many cases, whenthe thermostat malfunctions, one of more of its outputs goes into a highimpedance state or a float state or open circuit. When a thermostat isconnected directly to the air handler unit, a high impedance state or afloat state will not activate the HVAC relays or contactors andtherefore, the HVAC system will remain off.

There are products in the market that are connected between thethermostat and the air handler unit controllers that cannot handle afloating state as inputs. A common case is the thermostat fan outputsignal being in unknown state when the thermostat is switched to OFF.These products would read this as ON state, and will turn the fan on andrun continuously.

Therefore, there is a need to have a circuit to read any unknown orfloating signals from the thermostat fan, cool or heat command signal asknown 24 vac or 0 vac state. In this way, the fan, compressor or heaterwill always be turned off when it is not at an ON state. Further, itwould be desirable to provide a low cost controller installed betweenthe thermostat and the air handler that will work for the majority ofthe thermostats in the market, that it would solve the floating state ofthe thermostat output signal after the thermostat is turned off andkeeps the HVAC in OFF state, and that could be easily installed andoperated by the user.

The problems and the associated solutions presented in this sectioncould be or could have been pursued, but they are not necessarilyapproaches that have been previously conceived or pursued. Therefore,unless otherwise indicated, it should not be assumed that any of theapproaches presented in this section qualify as prior art merely byvirtue of their presence in this section of the application.

BRIEF SUMMARY OF THE INVENTION

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key aspects oressential aspects of the claimed subject matter. Moreover, this Summaryis not intended for use as an aid in determining the scope of theclaimed subject matter.

In an embodiment a new plug and play energy saving controller (ESC) isprovided to predict and extend the fan run time of HVAC systems afterthe heating or cooling unit has shut off and/or to stop the compressoror heater for a short duration of time if the compressor or heater hasbeen running continuously for a fixed period of time, but with the fanstill blowing. Thus, an advantage is the harnessing of otherwise wastedheating or cooling energy from the HVAC systems. Monitoring the previouscycle(s) for the compressor or heater on and off durations gives abetter, more intelligent, comprehensive and efficient fan extensionperiod, to save more energy. Further, shutting down the compressor orheater if they run continuously for, for example, 30 minutes, butkeeping the fan running, will act like a fan extension and it savesenergy.

In another embodiment, the new plug and play controller is insertedbetween the thermostat and the air handler unit. Thus, another advantageis the ease of installation of the controller.

In another embodiment the new plug and play controller is configured tochange the unknown state of the thermostat's fan, cool or heatcontroller circuitry into a known state when the thermostat is switchedto off or when the thermostat malfunctions. Thus, another advantage isthe increased versatility of the provided controller by making itcapable of functioning properly in connection with variousmanufacturers' thermostats.

The above embodiments and advantages, as well as other embodiments andadvantages, will become apparent from the ensuing description andaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For exemplification purposes, and not for limitation purposes,embodiments of the invention are illustrated in the figures of theaccompanying drawings, in which:

FIG. 1 illustrates a schematic circuit diagram of an integrated circuitfor controlling the fan, the compressor and the heater of a heating,ventilation and air conditioning (HVAC) system.

FIG. 2 illustrates a block diagram for controlling the fan, the heaterand the AC of a HVAC system using the integrated circuit from FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

What follows is a detailed description of the preferred embodiments ofthe invention in which the invention may be practiced. Reference will bemade to the attached drawings, and the information included in thedrawings is part of this detailed description. The specific preferredembodiments of the invention, which will be described herein, arepresented for exemplification purposes, and not for limitation purposes.It should be understood that structural and/or logical modificationscould be made by someone of ordinary skills in the art without departingfrom the scope of the invention. Therefore, the scope of the inventionis defined by the accompanying claims and their equivalents.

FIG. 1 illustrates a schematic circuit diagram of an integrated ESCcircuit 100 for controlling the fan, the compressor and the heater of aheating, ventilation and air conditioning (HVAC) system. Preferably, theintegrated circuit 100 comprises an input port 101 having a plurality ofinput terminals 101 and a plurality of output terminals 102, a voltageregulator 107, a microprocessor 103, transistors 109, 110, 111, 104, 105and 106, and triacs 112, 113 and 114, whereby at least one of theplurality of input terminals 101 switches the transistors 109, 110 or111 to a conducting state that turns on the microprocessor 103 whichcreates a trigger signal to turn on at least one of the plurality oftriacs 104, 105, 106 which provides an output 102 of circuit 100 thatenables the switching OFF or ON of at least one of the output terminalsto ground.

The plurality of input terminals 101 connects the integrated circuit 100to the thermostat of a HVAC system. The plurality of input terminals 101includes typically a first input terminal 115, a second input terminal116, a third input terminal 117, a fourth input terminal 118, and afifth input terminal 119. The input terminal 119 has typically a commonterminal voltage of 24 Vac with reference to the ground node of circuit100.

The input terminal 118 gets its input from the thermostat's red colorcoded wire. In circuit 100, the terminal 118 is at 0 vac with referenceto the ground node.

The input terminal 115 gets its input from the thermostat's fan outputline which is typically either a 24 vac or a 0 vac level. Sometimes,this line may be at floating state as described earlier. The inputterminal 116 gets its input from the thermostat's heat output line whichis either a 24 vac or a 0 vac levels. Sometimes this line may be in highimpedance state. The input terminal 117 gets its input from thethermostat's cool output line which is either a 24 vac or a 0 vaclevels. Sometimes this line may also be in high impedance state.

The voltage regulator 107 acts as a constant voltage source to provide aconstant voltage to the microprocessor 103 and the transistors 109,110,111, 104, 105 and 106.

The voltage regulator 107 is preferably fed from the output of a seriesof diodes 120 or diodes and current limiter 108. The capacitor 122 andZener diode 121 are connected in parallel to the voltage regulator 107.The capacitor 122 and the Zener diode 121 provide a constant voltage tothe voltage regulator 107. The capacitor 122 and the Zener diode 121 areconnected in parallel with a variable voltage source and acts as voltageregulators to regulate the voltage across the voltage regulator 107. TheZener diode 121 clamps the voltage to the maximum specified voltageacross the input terminal of the voltage regulator 107. The integratedcircuit 100 has a parallel pair of output capacitors 123 to maintain thevoltage regulator 107 output supply voltage.

The microprocessor 103 has a plurality of terminals 124 to providetriggering signals to the base of transistors 104, 105 and 106.Transistors 104, 105 and 106 are acting as drivers to provide drivesignals to turn on or off the triacs 112, 113 and 114. The outputterminals 102 are the outputs of triacs 112, 113 and 114.

As an alternate embodiment, the triacs 112, 113 and 114 can be replacedwith any switchers, such as relays, contactors or multiplexers.

The plurality of output terminals 102 connects the integrated circuit100 to the air handler unit of a HVAC system. The plurality of outputterminals 102 includes a first output terminal 124, a second outputterminal 125, a third output terminal 126, a fourth output terminal 127,and a fifth output terminal 128. The output terminal 128 has a commonterminal voltage of 24 vac with reference to circuit 100's ground node.The output terminal of 127 is the red color coded wire which is at 0 Vacwith reference to circuit 100's ground.

The output terminal 124 goes to the air handler unit's fan input. Outputterminal 125 to the air handler unit's heat input. Output terminal 126to the air handler unit's cool input.

The turn on or turn off actions of the triacs 112, 113 and 114 willenable output terminals 124, 125 and 126 to be connected to ground or bein high impedance state. These in turn will control the operations ofthe air handler unit's solenoids to activate or deactivate thecontactors or relays of the blower fan, compressor and gas/electricheater.

The plurality of terminals 124 of the microprocessor 103 includes asupply voltage terminal 129, a ground terminal 130, drive outputterminals 131, 132, 133, and input terminals 134, 135, 136.

Terminal 134 of microprocessor 103 is driven by the collector oftransistor 111 and the output of a control circuit derived from theinput 117. This control circuit includes resistor 137, the output ofvoltage regulator 107, resistor 138, reverse biased diode 139, resistor142, input 117, a pair of parallel resistors 143 and the input (common)terminal 101.

Similarly, terminal 135 of microprocessor 103 is driven by the collectorof transistor 110 and a control circuits derived from the input 116.

Similarly, terminal 136 of microprocessor 103 is driven by the collectorof transistor 109 and a control circuits derived from the input 115.

Transistors 109, 110 and 111 are npn transistors that act as switchingelements and together with outputs derived from the inputs 116, 117 and118 are connected to the microprocessor 103 to manipulate the outputsignals.

The base of transistor 111 is connected to input (cooling) terminal 117and input (common) terminal 119, by a pair of parallel resistors 143 inseries with resistor 142 and in series with diode 139, in series withresistor 140 and diode 141. The base of the transistor 111 has acapacitor 144 and a resistor 145 connected across and to ground. Thecollector of the transistor 111 provides the input to terminal 134 ofthe microprocessor 103 which controls the output (cooling) terminal 126.The emitter of transistor 111 is connected to circuit 100 ground.

Similarly, the same logic circuits applies for input (heater) terminal116 to control the output (heater) terminal 125, and for input (fan)terminal 115 to control the output (fan) terminal 124.

The integrated circuit 100 has the diodes 120 in forward bias and diodes139, 146 and 147 in reverse biased. The circuit 100 enables switchingthe HVAC fan to OFF if the thermostat fan output is in OFF or float orunknown state. Similarly, the circuit 100 enables switching the HVACheater to OFF if the thermostat heat output is in OFF or float orunknown state. Similarly, the circuit 100 enables switching the HVACcooling compressor to OFF if the thermostat cool output is in OFF orfloat or unknown state.

The circuit 100 process the float state of the thermostat output signalsas it enters into circuit device 100 through input terminals 115, 116and 117 and then outputs an OFF state signal in output terminals 124,125 and 126.

The microprocessor 103 is programmed for energy efficient operation ofthe HVAC system by extending the fan run time of the HVAC blower fanbased on the energy left over in the heater elements or in the airconditioning cooling coil and/or the rate of energy transfer (i.e., howfast the room gets heated up again in the case of a cooling cycle, orhow fast the room gets cooled down again in the case of a heatingcycle), as it will be described in more details hereinafter. The rate ofenergy transfer may be obtained by monitoring the on-off periods ofprior cycles to estimate temperature differences between inside andoutside and thus the rate at which the room is heated up or cooled downby its environment during the OFF period after the thermostat sends acommand signal to have the HVAC fan shut off. Additionally, if thecompressor (or heater, if HVAC system is in heating mode) has beenrunning continuously for a predetermined period, for example,approximately 20-30 minutes, the microprocessor 103 will shut down theHVAC compressor (or heater) for, for example, 3 to 5 minutes while thefan continues to run, even though the thermostat did not sent a commandsignal to have the compressor (or heater) shut down. The above twoactions (i.e., extending fun run time and shutting the compressor orheater briefly) are independent of each other and controlled by themicroprocessor 103. Shutting down the compressor or heater if they runcontinuously for, for example, 30 minutes, but keeping the fan running,will act like a fan extension and it saves energy.

The input terminal 115 voltage changes depending on the ON/OFF positionof the fan. The first input terminal 115 is coming from the thermostatfan output command signal (color coded green wire) and has a voltageselected from a group consisting of 24 vac, 0 vac and a floating value.The floating value means that the input terminal 115 is not connected toeither 24 vac or 0 vac, and can assume any value. The input terminal 119always has a common terminal voltage of 24 vac with reference tocircuit's 100 ground.

In a typical operation of a thermostat, a 24 vac thermostat output is anOFF state and ground or 0V thermostat output is an ON state. So, thethermostat turns on the fan by outputting a 0 vac to the fan wire, etc.When the thermostat wants to turn OFF the fan, the input (fan) terminal115 of circuit 100, and the input (common) terminal 119 of circuit 100both has 24 vac. The reversed biased diode 147 allows negative portionof the 24 vac from input terminal 115, after passing through resistor155, to be present at the anode of diode 147. The RMS voltage at theanode of diode 147 derived from input terminal 115 in series withresistor 155, is at least a negative 10 Vrms. From input (common)terminal 119, approximately 5 VDC from the voltage regulator 107 inseries with resistor 148, is also present at the anode of the diode 147.The resultant of the RMS voltage and the DC voltage is always negativewhich charges the capacitor 149 with a negative voltage as well. Thediode 150 blocks this voltage from the base of transistor 109. Theresistor 151 pulls the voltage of the base of transistor 109 to groundand cause the transistor 109 to be in off state. So, the input terminal136 to microprocessor 103 is approximately 5 vdc high from the output ofvoltage regulator 107 in series with resistor 153. The microprocessor103 will manipulate its output 131 to low (0 volt) causing transistor106 to shut off. This in turn shuts off the triac 112 and causes thecircuit 100's fan output terminal 124 to be in high impedance statewhich turns the HVAC fan to off.

When the input terminal 115 has 0 vac or ground, and the input (common)terminal 119 has 24 vac, the 24 vac of terminal 119 in series withresistor pairs 156 sinks to ground as the outputs of resistor pair 156is connected to the input terminal 115 which has 0 vac.

The anode of reverse bias diode 147 is now high from the 5 vdc throughresistor 148. The positive voltage at the anode of diode 147 cause thecapacitor 149 to be charged to a positive voltage which in turn causethe forward bias diode 150 to conduct and turns on transistor 109. Whentransistor 109 conducts, the microprocessor 103's terminal 136 becomeslow. Microprocessor 103 manipulates its output 131 to high and turns ontransistor 106 which in turn turns on triac 112. The circuit 100'soutput (fan) terminal 124 becomes 0 vac which turns on the fan of theHVAC system.

When the circuit 100's input terminal 115 is in floating state, theinput 115 is not connected to either 24 vac or 0 vac. In the floatingstate, the voltage at terminal 115 is unknown. The voltage at terminal119 has 24 vac flowing through the pair of parallel resistor 156. Thereverse bias diode 147 allows negative portion of this 24 vac to bepresent at the anode of diode 147 which will charge the capacitor 149 toa negative voltage. The diode 150 blocks the negative voltage to thebase of transistor 109, and the resistor 151 pulls the base oftransistor 109 to ground turning transistor 109 to off state. This inturn cause a 5 vdc present at terminal 136 of microprocessor 103 whichcause 131 to go to low voltage shutting off transistor 106 and puttingthe triac 112 to off state. The circuit 100's output (fan) terminal 124stays at high impedance state and the HVAC's fan is at OFF state therebysolving the problem of the floating inputs into terminal 115.

Similarly, the above applies to circuit 100's input (heater) terminal116 and input (cooling) terminal 117 which can solve the floating statesto these inputs.

FIG. 2 illustrates a block diagram of an integrated circuit 201 forcontrolling the fan 203, heater 204 and AC 205 of a HVAC Air HandlerUnit 200. The integrated circuit's 201 configuration, and morespecifically that of its controller 218, may be as that of theintegrated circuit from FIG. 1. The HVAC 200 includes an air conditioner(AC) 205, a heater 204 and a fan 203 and the wire color coded green withits terminal 206, wire color coded white with its terminal 207, wirecolor coded yellow with its terminal 208, wire color coded red with itsterminal 209, and a 24 VAc common wire and its terminal 210.

The integrated circuit 201 is as shown connected between the thermostat202 and the HVAC air handler unit 200. The integrated circuit 201includes output connectors 211, input connectors 212 and the controller218. The output connectors 211 have wire lead terminals or screwsterminals 214, 213, 215, 216 and 217 to connect to the HVAC 200. Theinput connectors 212 have wire lead terminals or screw terminals 222,223, 221, 220 and 219 to connect to the thermostat.

From the output connector 211, the wire from the G terminal 214 isconnected to the G terminal 206 of HVAC 200, wire from W terminal 213 isconnected to the W terminal 207 of HVAC 200, wire from Y terminal 215 isconnected to the Y terminal 208 of HVAC 200, wire from C terminal 216 isconnected to the C terminal 210 of HVAC 200 and the wire from R terminal217 is connected to the R terminal 209 of HVAC 200.

From the input connector 212, the wire from the G terminal 222 isconnected to the G terminal 224 of thermostat 202, wire from W terminal223 is connected to the W terminal 225 of thermostat 202, wire from Yterminal 221 is connected to the Y terminal 226 of thermostat 202, wirefrom C terminal 220 is connected to the C terminal 227 of thermostat 202and the wire from R terminal 219 is connected to the R terminal 228 ofthermostat 202.

When the thermostat 202 sends any control command instructions throughits fan, heat or cool outputs, these instructions go into the integratedcircuit 201, which acts as an energy saving controller (ESC) bymanipulating these instruction and sending a revised set of energysavings command instructions to the HVAC 200, as disclosed herein.Further, the integrated circuit 201 continuously monitors the status ofthe thermostat 202, and will turn off the fan, heater or compressor ifit detects a float or high impedance state of thermostat 202 due to avariety of reasons.

The ESC will adjust the fan operation automatically for heating using analgorithm derived from the stored energy left after furnace or heat pumphas shut down and the rate at which the condition of the room is changedby its environment after the heater or air conditioning are in OFFcondition. The algorithm will preferably be based on how long the heaterhas been running, and how long the heater was shut off (on off and oncycle) after the set temperature has been reached, in the first cycle,and then predict for the next cycle, how long the fan should continue torun based on the data from the previous cycle(s) and preferably thecurrent cycle. So, the fan run time extension is preferably alwayspredicted considering the data from the previous one on-off-on cycle orprevious multiple on-off-on cycles.

When the thermostat calls for heat, the thermostat heat or ‘W’ output225 in FIG. 2. goes typically to 0 vac. This makes the input 116 in FIG.1 goes to 0 vac as well. The voltage regulator 107 output will create apositive DC voltage at the anode of diode 146, charges up capacitor 161and create a positive DC voltage at the base of transistor 110. Thisturns on the transistor 110, and cause input 135 to microprocessor 103to be at 0 vac or low voltage state. The microprocessor 103 will thenmake output 133 go to approximately 5 vdc or high voltage state. Whenoutput 133 is in high voltage state, transistor 104 turns on, and theregulator's 107 output through resistor 165 activates triac 114 which inturn pulls heater output 125 to 0 vac. Heater output 125 in FIG. 1 isthe same connection as output connector 213 of 201 in FIG. 2. Output 125of FIG. 1 is therefore connected to heater input ‘W’ 207 of FIG. 2. Thisturns on the heater 204 of HVAC 200 in FIG. 2. In a HVAC system, ifheater is a gas heater, the thermostat will not turn on the fan whenthere is a call for heat. If the heater is an electric heater or a heatpump, the thermostat will also turn on the fan when there is a call forheat.

Assuming an electric heater, when there is a call for heat, thethermostat fan or “G” output 224 in FIG. 2 goes to 0 Vac. Since 224 ofFIG. 2 is connected to 222, which is the same terminal as input 115 ofFIG. 1, this makes the input 115 goes to 0 vac as well. This in turnturns on transistor 109, and cause input 136 to microprocessor 103 to beat low voltage state. The microprocessor 103 will then make output 131go to high voltage state. When 131 is in high voltage state, transistor106 turns on, and triac 112 is activated. This cause fan output 124 ofintegrated circuit 100 to go to 0 vac. Fan output 124 of FIG. 1 is thesame connection as terminal 214 of FIG. 2, which is connected to 206 andturns on the fan 203 of HVAC 200.

As described above, when there is a call for heat by the thermostat, theinput 135 in FIG. 1 goes into a low voltage state. The microprocessor103 records the duration of input 135 in low voltage state which is theheater ON time. When the room temperature has reached its upperhysteresis set temperature, the thermostat 202 heater output terminal225 in FIG. 2 goes to 24 vac. This in turn makes input terminal 116 ofFIG. 1 goes to 24 vac and turns off transistor 110, and cause input 135be in high voltage state. The microprocessor 103 then causes its output133 to low voltage state which turns off the heater. In addition,microprocessor 103 also record the duration of input 135 in high voltagestate which is the heater OFF time. The software in the microprocessor103 stores the data of heater previous cycle(s) ON time (input 135 inlow voltage state), and heater previous cycle OFF time (input 135 inhigh voltage state) and the heater current cycle ON time. Then, at theend of the current heater ON cycle which is the next time this line 135transitions from low to high voltage, the microprocessor 103 takes theprevious cycle's heater ON time and Off time and the current ON time,and computes or predicts how long its output 131 (which controls thefan), should continue to remain at high voltage state to keep the fan ONat the end of current heater ON time.

Since the heater element in the heat exchanger gets to its maximumtemperature fairly quickly (e.g., 7 minutes), by the microprocessormeasuring the heater ON time it can be determined if the heater hasreached its maximum temperature. After the heater elements have shutoff, the microprocessor can estimate how much residual energy is leftthat can still be used to heat up the room, which determines with howmuch the fan run time should be extended.

In addition, the heater OFF time during the ON-OFF-ON cycle(s) indicatesthe rate at which the room cools down after the heater is OFF and thisdepends on the temperature difference between the room and the outsideambient and the environment of the room such as wall insulation, numberof living occupants, heat generating appliances (electronic orelectrical equipment, lights, computers, TV, etc.), and so on. If theheater OFF time is short, the fan extended run time should also be shortas it takes faster for the residual heat energy left at the heatexchanger to cool down as well. This also will prevent cool air fromcirculating in the room.

As an example, if the room set temperature is 75° F. (75° F.+/−1° F. ashysteresis), and the outside temperature is 60° F., the heater may runfor 20 minutes to get the room reached (76° F.). The heater then shutsoff for let's say 10 minutes for the room to drop the temperature downto 74° F. and then it turns on again for let's say 15 minutes. Fromexperiments we have conducted it was determined that all furnacesreached their maximum temperature after 7 minutes of burning. Thefurnace control board will usually let the fan continue to run for 90seconds after it has shut down. We shall call this the default fan runtime extension. So, an exemplary algorithm is to measure if this 7minutes has been reached, and assign a 1 (one) minute fan extension, ifit has been reached. For the 10 min of heater off, a 20% may be assignedas time extension, or 2 min. For the current heater ON time of 15 min(i.e., over 7 min), another 1 minute may be assigned as time extension.So the total fan time extension is 4 (four) minutes in this example. Thealgorithm can then compare this total time to see if it is above thedefault extension time of 90 seconds, and if it is, then it will extendthe fan run time with an additional 4 minutes minus 90 seconds, or 2.5minutes additional fan run time. In the above example, if the heater wasOFF for 6 minutes instead of 10 minutes, then the total fan timeextension would be 1 min+1.2 min+1 min, which is 3.2 minutes. In thiscase, the software will ask the fan to extend for 3.2 min minus 90seconds, or 1.7 minutes additional fan run time.

In addition, to increase the efficiency of the system even further, ifthe HVAC's heating elements have been operating continuously for aperiod of time (e.g., 20-30 minutes), they will be made by the ESC toshut down for a short period of time (e.g., 3-5 minutes) with the fanstill running, to not only reduce the furnace temperature thereforeextending its life, but also harvest some residual heat energy for theconditioned room.

For air conditioning, the same ESC will adjust fan operationautomatically for cooling using an algorithm derived from the storedenergy left in the water condensed on the cooling coils and the rate atwhich the room gets heated up, which depends on a number of factorsincluding the room's insulation, number of occupants in the room, numberof appliances operating in the room, temperature difference between theroom and the outside ambient, etc., after the air conditioner has shutdown. The algorithm will preferably be based on how long the compressorhas been running, and how long the compressor was shut off (on-off-on)in previous cycle(s). When the thermostat calls for cool, in FIG. 2,thermostat 202 output 226 will go to 0 vac. Since output 226 isconnected to terminal 221 of 201 which is the same as input 117 in FIG.1, the anode of diode 139 has a positive DC voltage from the output ofregulator 107, through resistor 138 and charged up the capacitor 144 andturns on transistor 111. This in turn makes input 134 of microprocessor103 to become low voltage state. Microprocessor 103 in turn will causeits output 132 go to high voltage state. Then, transistor 105 get turnedon, and triacs 113 activated. This in turn causes cooling terminal 126be in 0 vac which make terminal 215 in FIG. 2 go to 0 vac as well. Thisthen turns on the AC compressor 205 of the HVAC 200. Also, when thethermostat calls for cool, the fan output 224 of thermostat 202 is alsoin 0 vac which cause the fan 203 of HVAC 200 to be turned on as well.The microprocessor 103 records the duration of its input 134 in lowvoltage state (AC compressor ON) and in high voltage state (ACcompressor OFF). Then, at the end of the next compressor ON cycle, thesoftware makes its output 131 which controls the fan, to stay on for apredicted period of time after the end of the compressor ON period. Thiscontinues on, cycle after cycle, with the fan extension period based onthe data from the previous compressor ON and OFF cycle(s) and current ONcycle. The predicted fan extension run time is computed by the softwarethat uses the data of the previous cycle(s)′ compressor ON, OFF and ONduration (see example below).

For example, based on an average air humidity of 50%, after thecompressor has run for 20 minutes, the average AC condenser coil istypically dripping wet. This will be equivalent to maximum latentcooling energy, which is available when the water condensed in the coilis evaporated away. With fan blowing, it takes typically approximately 5to 7 minutes to evaporate the water to dry with a 50% air humidity. So,by measuring how long the compressor is ON and assuming an average of50% humidity for example, the ESC can extrapolate the estimated theavailable energy, and thus, how long the fan run extension should be,from the partially wet condenser coils if the AC is ON for less than 20mins. For example, if the compressor has run for 10 minutes and the airhumidity is 50%, the fun extension time may be 3 minutes. With the dataon how long the AC compressor was OFF before it kicks on again, ESC canadjust this fan extension time further (see example below). It should benoted that this is for the situation when the compressor is ON for lessthan preferably 30 minutes continuously. If the compressor was ON forpreferably 30 minutes, the microprocessor will shut down the compressorregardless if the room temperature has been reached or not, but keep thefan running for the next cycle.

Again, by monitoring the compressor ON time and compressor OFF time, theESC also obtains an indication of the difference between the roomtemperature and the outside air temperature and the rate at which theroom is heating up after the compressor is OFF.

For example, if the outside temperature is 100 degrees Fahrenheit (° F.)and the room set temperature is 75 degrees F. (assume a hysteresis of+/−1 degrees ° F.), the compressor could be running for 20 minutesbefore the room reached the 74 degrees F. (75° F.−1° F. hysteresis) andthen the compressor goes to OFF maybe for 5 minutes. After thecompressor is OFF, then the room will get heated up relatively fast dueto 100 degrees F. outside. So, when the room temperature gets to 76degrees F. (75° F.+1° F. hysteresis), the compressor is ON again andlet's assume for 10 minutes before it reaches the set temperature again.The fan time extension algorithm may be to take 10% of previous ONperiod, which is 2 minutes (“mins”), plus 20% of the previous OFFperiod, which is 1 min, plus 20% of the current ON period which is 2mins totaling 5 mins, which would mean to extend the fan run for 5 minsat the end of the current compressor ON time. However, if the outsidetemperature is only 85 degrees F., then, it takes longer for the room tobe heated up to 76 degrees F. In this case, the compressor OFF time ismaybe 7 minutes; and let's assume the compressor is ON again for 10 minsafter that. So, the algorithm for fan extension at the end of thiscurrent 10 mins compressor ON time may be 2 min plus 1.4 min plus 2 minwhich total 5.4 minutes. So, by measuring the compressor ON time, andcompressor OFF time, the ESC can estimate the temperature differencebetween outside air and room air, and the rate at which the room getsheated up after the compressor is OFF from other temperature changingactivities in the room, thus, how long the fan extension run time shouldbe. Thus, shorter fun extension run times will apply when the differencebetween the room temperature and the outside air temperature is greater,and vice versa.

If the HVAC's cooling elements have been operating continuously for aperiod of time (e.g., 20-30 minutes), they will be made by the ESC toshut down for a short period of time with the fan still running (e.g.,3-5 minutes) to harness the stored energy left in the water condensed onthe cooling coil.

Hence, the ESC recovers and delivers more heating and cooling energy tothe conditioned space than is possible with original controls from thethermostat. The ESC improves the efficiency of HVAC equipment bydelivering additional heating or cooling capacity for a small amount ofadditional electric energy (kWh) utilized by the fan.

Air conditioners cool conditioned spaces by removing sensible and latentheat from the return air which reduces the supply air temperature andhumidity. Latent heat is removed as water vapor is condensed out of theair due to the temperature of the evaporator coil being less than thereturn air dew point temperature. Latent heat is the quantity of heatabsorbed or released by air undergoing a change of state, such as watervapor condensing out of the air as water onto a cold evaporator coil orcold water evaporating to water vapor which will cool the air.

Most evaporators are cold and wet (below 40 to 50° F.) after thecompressor turns off. Cooling energy left on the evaporator coil afterthe compressor turns off is generally wasted. The evaporator absorbsheat from its surroundings and cold water on the coil flows down thecondensate drain.

Again, the ESC as disclosed herein, recovers the remaining coolingenergy from evaporator coil by operating the fan after the compressorturns off to cool the conditioned space. In addition, after thecompressor has been running for a period of for example approximately20-30 minutes, the evaporative coil is cold and wet, and by shuttingdown the compressor while keeping the fan running for, for example, 3-5minutes, the water evaporating away at the evaporative coil cools downthe incoming air flow from the ducting.

Again, most furnace heat exchangers are still hot (above 135 to 210° F.)after the furnace fan turns off. The ESC recovers the remaining heatenergy from the hot furnace heat exchanger after the furnace turns offand delivers this heat to the conditioned space. In addition, after theheating element has been running for a period of for exampleapproximately 20-30 minutes, the hot heat exchanger is at its maximumtemperature, and by shutting down the heating element while keeping thefan running for, for example 3-5 minutes, the residual heat energy stillheats up the incoming air flow from the ducting.

Again, as described earlier when referring to FIG. 2, the ESC works bypreferably disconnecting from the original thermostat, all the originalwires that come from the air handler unit, and re-connecting all thesewires to the ESC module. A set of duplicate wires from the ESC is thendirectly connected to the thermostat (see FIG. 2).

When the thermostat sends out to the fan, compressor and heater signals,they now all go to the ESC. The ESC reads the signals from these wirescoming from the thermostat and automatically sends out the desiredsignals described herein to the air handler unit that controls the HVAC.

Again, the ESC uses preferably all the outputs of the thermostat as itsinputs. The command signal from the thermostat may be either a high of24 vac or 0 vac (ground) or sometimes in floating state.Correspondingly, the ESC is configured to accept either 24 vac or 0 Vacor float state as its inputs so that it can interface with everymanufacturer's thermostats used in HVAC systems.

In another embodiment, a temperature sensor (not shown) can be installedin association with the ESC to sense the temperature of the outside air.The ESC can be installed inside the house next to the thermostat, or atthe air handler in the garage or attic or outside the building on theroof for roof top units (RTU). If the ESC is installed inside the house,a remote temperature probe can be installed outside the house andsending the information to the ESC by RF signal. The purpose of thistemperature sensor will be described hereinafter.

In yet another embodiment, the reversing valve signal from thethermostat may be read by the ESC. The reversing valve is identified asO/B terminal on the thermostat. In FIG. 2, the input terminals 212 willhave an additional terminal (shown in FIG. 2 as unconnected terminal) toconnect to the thermostat's reversing valve O/B output (not shown inFIG. 2). The ESC can read this output to do the following functionality.For heat pump HVAC system, the compressor is used in reverse to provideheat to the rooms. In this case, the ESC will read the reversing valveoutput (O/B) from the thermostat, and will preferably either disable theextend fan run time, or extend the fan run time to for example 25% ofits programmed duration after the heat pump (compressor) has completedits cycle. For example, if the outside temperature is below 40 degreesCelsius (C), the additional fan run time or the compressor shut downwith fan running may bring in very cold air. Therefore it would bedesirable to install a temperature sensor in association with the ESC tobypass the energy saving features described earlier in this disclosureif the outside temperature is sensed to be below a predetermined level(e.g., 40 degrees C.).

Also, preferably, for the heat pump mode, the ESC will not shut down theheat pump (compressor) for a few minutes after a continuous run of forexample 20-30 minutes, to ensure no cold air is blowing into the room.

In another embodiment, a humidity sensor can be installed in inassociation with the ESC to sense the humidity of the outside air if theESC is installed at the roof top, or the inside room air if the ESC isinstalled inside the building. During the summer, in some months andsome parts of the country, the humidity could be for example over 75percent. Since the energy saving feature of the ESC is based on therecovery of latent energy from evaporating away the water condensed ontothe cooling coil, when the humidity is very high, the condensed watercannot be evaporated away. In addition, blowing high humidity air intothe room with the compressor off is uncomfortable for many people.Therefore it would be desirable to install a humidity sensor in the ESCto bypass the energy saving features if the outside humidity is forexample over 75% or the inside humidity is over for example 65%. Thisbypass feature can be factory programmed or user programmed depending onthe user's choice.

The apparatus and methods disclosed herein are suitable for split typecentral HVAC's or independent heater and compressor systems.

It may be advantageous to set forth definitions of certain words andphrases used in this patent document. The terms “include” and“comprise,” as well as derivatives thereof, mean inclusion withoutlimitation. The term “or” is inclusive, meaning and/or. The phrases“associated with” and “associated therewith,” as well as derivativesthereof, may mean to include, be included within, interconnect with,contain, be contained within, connect to or with, couple to or with, becommunicable with, cooperate with, interleave, juxtapose, be proximateto, be bound to or with, have, have a property of, or the like.

As used in this application, “plurality” means two or more. A “set” ofitems may include one or more of such items. Whether in the writtendescription or the claims, the terms “comprising,” “including,”“carrying,” “having,” “containing,” “involving,” and the like are to beunderstood to be open-ended, i.e., to mean including but not limited to.

Throughout this description, the embodiments and examples shown shouldbe considered as exemplars, rather than limitations on the apparatus andprocedures disclosed or claimed. Although many of the examples involvespecific combinations of method acts or system elements, it should beunderstood that those acts and those elements may be combined in otherways to accomplish the same objectives. With regard to flowcharts,additional and fewer steps may be taken, and the steps as shown may becombined or further refined to achieve the described methods. Acts,elements and features discussed only in connection with one embodimentare not intended to be excluded from a similar role in otherembodiments.

For means-plus-function limitations recited in the claims, the means arenot intended to be limited to the means disclosed in this applicationfor performing the recited function, but are intended to cover in scopeany means, known now or later developed, for performing the recitedfunction.

Further, in describing representative embodiments of the presentinvention, the specification may have presented the method and/orprocess of the present invention as a particular sequence of steps.However, to the extent that the method or process does not rely on theparticular order of steps set forth herein, the method or process shouldnot be limited to the particular sequence of steps described. As one ofordinary skill in the art would appreciate, other sequences of steps maybe possible. Therefore, the particular order of the steps set forth inthe specification should not be construed as limitations on the claims.In addition, the claims directed to the method and/or process of thepresent invention should not be limited to the performance of theirsteps in the order written, and one skilled in the art can readilyappreciate that the sequences may be varied and still remain within thespirit and scope of the present invention.

Although specific embodiments have been illustrated and described hereinfor the purpose of disclosing the preferred embodiments, someone ofordinary skills in the art will easily detect alternate embodimentsand/or equivalent variations, which may be capable of achieving the sameresults, and which may be substituted for the specific embodimentsillustrated and described herein without departing from the scope of theinvention. Therefore, the scope of this application is intended to coveralternate embodiments and/or equivalent variations of the specificembodiments illustrated and/or described herein. Hence, the scope of theinvention is defined by the accompanying claims and their equivalents.Furthermore, each and every claim is incorporated as further disclosureinto the specification and the claims are embodiment(s) of theinvention.

What is claimed is:
 1. A method for controlling an air handler includinga fan and an HVAC component which is a member of the group consisting ofa heater and a compressor, the method comprising: installing an energysaving controller between a thermostat and the air handler, monitoringby the energy saving controller of ON and OFF durations of the HVACcomponent in a first cycle and of ON duration of a second cycleimmediately following the first cycle, and determining the fan's firstrun time extension amount in the second cycle based on the ON and OFFdurations of the first cycle and the ON duration of the second cycle,wherein determining the fan's first run time extension amount comprisesmultiplying a predetermined first percentage to the first cycle ONduration, multiplying a predetermined second percentage to the firstcycle OFF duration, multiplying a predetermined third percentage to thesecond cycle ON duration, and adding resulting time amounts.
 2. Themethod of claim 1, further comprising subtracting a default fan run timeextension amount from a sum obtained by the adding of the resulting timeamounts.
 3. The method of claim 1, wherein, in the cooling mode, thepredetermined first percentage is about 10%, and wherein thepredetermined second percentage and the predetermined third percentageare both equal to about 20%.
 4. The method of claim 1, wherein in theheating mode, the predetermined first percentage is about 10%, whereinthe predetermined second percentage is about 20% and wherein thepredetermined third percentage is about 7%.
 5. The method of claim 1,further comprising shutting down the HVAC component for a firstpredetermined duration and overriding determining of the fan's first runtime extension amount if the HVAC component has run continuously for asecond predetermined duration during the second cycle, while allowingthe fun to run for a fan's second run time extension amount equal withthe first predetermined duration.
 6. The method of claim 5, wherein thefirst predetermined duration is about 3-5 minutes and the secondpredetermined duration is about 20-30 minutes.
 7. The method of claim 1,further comprising disconnecting from a thermostat's connectors allwires that come from the air handler, connecting all the wires to thecorresponding energy saving controller's output connectors, andconnecting a set of energy saving controller input connectors to thethermostat connectors.
 8. The method of claim 1, wherein the energysaving controller is configured to accept either 24 VAC, 0 VAC orunknown signals as its inputs for the HVAC component and the fan.
 9. Themethod of claim 8, further comprising shutting down the HVAC componentor the fan when their corresponding input signals are unknown.